In the Trenches

Before all else!

You’ve heard it a hundred times, but it’s worth repeating: Before you trench any site, have the location of existing subsurface utility lines confirmed and marked. If you don't already know the number to call in your location, the website www.digsafely.com provides links to many marking services around the country.

Trencher anatomy

The two basic types of compact trenchers are ride-on and walk-behind. Walk-behind units are smaller and more appropriate for tight spaces. Most trenchers of either type have three basic operation systems:

  • The ground drive, which enables you to transport the machine and drives the machine while trenching.
  • Trenching articulation, including on-off, drive traction, and boom and chain-drive controls.
  • A spoil-handling auger that windrows trenched soil adjacent to the trench for easy backfilling.

Beyond this, machines vary widely in terms of the number and sophistication of options. Your choices include the type of chain and boom controls, digging depth and width, horsepower, safety features and many other options.

Some of the most basic compact trenchers—disc trenchers or, as some manufacturers call them, earth saws—use a motor-driven spinning disc with digging teeth. These typically produce narrow, shallow trenches, so their use is limited to smaller applications. However, they are adequate for small piping as well as some wiring, and their price and size make them economical options for small-scale uses.

The chain and teeth

The chain is a critical component of any trencher. Regardless of which trencher you ultimately select, chain options let you vary trench width or adapt to specific soil qualities or constraints. By selecting the right combination of teeth, you can overcome most soil challenges including tree roots, troublesome fill material (sub-surface building debris, paving pieces), extremely sandy soils (which are especially difficult on slopes), soils with cobblestone-size or larger aggregates and clay soils, both hard and mucky.

The teeth of the chain do the actual digging. Most trencher chains employ cup teeth, which may comprise some or all of the teeth of the chain. As the name implies, cup teeth efficiently scoop out dirt from the trench. In relatively soft soil, cup teeth alone are adequate for most jobs and may be vital in sandy soil.

A few manufacturers make chains with sharp carbide teeth designed for breaking through tougher soil or soil with buried debris. This increases production, particularly in hard ground. However, an additional benefit of carbide teeth's greater durability is extended life span in normal digging conditions. That makes carbide teeth popular with equipment rental companies.

Some carbide teeth are welded directly to the chain whereas other teeth, carbide or cup, bolt onto the chain. When bolt-on teeth wear down or break, you simply bolt on new ones. Chains that have teeth welded directly to the chain must be repaired by welding.

You can devise various combinations of cup and carbide teeth for optimum performance in certain digging conditions, an easier matter with bolt-on teeth than with welded teeth. Some operators add hard facing to cup teeth to lengthen their lifespan, but it is possible that this could decrease digging performance. Trencher manufacturers usually offer you a variety of chain and teeth options on new models as well as for replacement parts.

Proper chain tensioning is the "golden rule" of trenchers. Similar to chainsaws, trencher chains must be neither too tight nor too loose. Poorly adjusted chains wear out much more quickly. Experienced operators develop a "feel" for proper chain tension. However, trencher owner manuals usually provide specifications for chain tension. You should check and adjust chain tension periodically during operation because chains stretch with normal use and require tightening to maintain proper tension.

Chains, regardless of the condition of the teeth, eventually will need replacement. The manufacturer should be able to provide some guidance in this regard. For example, Ditch Witch recommendations state that when a chain stretches more than 3 percent of its compressed length, it's time for a new one. Determine this by laying the chain on a level surface and pushing from the ends so that you remove all the slack. Measure its length. Then stretch the chain by pulling its ends and measure its length once more. If the stretched length is more than 3 percent longer than the compressed length, replace the chain. Sprockets also may need periodic replacement due to normal wear.

Trencher chains are designed to operate "dry," so oiling trencher chains is not a recommended practice. Oil actually can increase wear because it attracts dirt particles and causes them to stick to the chain.

Safety

Remember that safety is a concern with trenchers as with all power equipment. When you operate a trencher, avoid loose clothing that could catch in moving parts, and always wear eye protection. Do not remove protective shields or disconnect safety switches, and make sure the engine is turned off before performing any adjustments or maintenance.

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© 2016 Penton Media Inc.

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